The present invention relates to carbon foams and methods of making carbon foams as well as their use in a variety of products, such as insulation materials and capacitors.
Carbon aerogels have been used in a wide variety of applications, including thermal insulation, conducting fillers for polymers or plastics, electrodes, and electrochemical cells. Carbon aerogels which have high surface areas and high DBP values are desirable in many of these and other applications.
Various methods are known to make carbon aerogels including using pitch, using organic gels with a catalyst and reacting the mixture, using sol-gel polymerization to form highly cross linked networks of high surface area foam and dissolving a polyacrylonitrile in a heated solution with at least one alkali metal halide in a solvent to eventually form a liquid gel. The liquid gel is then heated wherein the solvent is removed along with the dissolved alkali metal halide to provide a porous form consisting essentially of polyacrylonitrile wherein the porous form is then cured at elevated temperatures to carbonize the polyacrylonitrile to form the carbon foam.
While such methods are useful, there is always a desire in the industry to develop other less expensive methods of making carbon foams which preferably lead to greater flexibility in making foams having higher surface areas as well as high structure.
A feature of the present invention is to provide carbon foams.
Another feature of the present invention is to provide carbon foams preferably having high surface areas as well as high structure.
An additional feature of the present invention is to provide methods of making carbon foams.
Still, another feature of the present invention is to incorporate the carbon foams into such applications as thermal insulation, elastomer or plastic reinforcement, conducting fillers, electrodes, and the like.
Additional features and advantages of the present invention will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. The objectives and other advantages of the present invention will be realized and obtained by means of the elements and combinations particularly pointed out in the written description and appended claims.
To achieve these and other advantages, and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention relates to a method of making carbon foam which involves pyrolizing a mixture which contains at least one pyrolizable substance and at least one unpyrolizable material and then removing the unpyrolizable material to obtain the carbon foam.
The present invention further relates to carbon foam made by the above-described method.
The present invention further relates to carbon foam having cells bordered by thin sheets or windows and/or struts. The foam particles are typically about 5 to about 30 microns across and the cells are from about 0.5 and to about 3 microns across. Typically the cells are not closed, but have openings between them. Because the foam can be rigid, pieces of the foam can be broken off, and the material can contain both the foam particles and their fragments.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide a further explanation of the present invention, as claimed.